An example is a motor vehicle having an internal combustion engine as prime mover and propelling the vehicle as load.
The vehicle is provided with a gear box between the engine and the load to provide torque conversion enabling the engine to run in a power output range and at a speed of revolution range in which the engine operates efficiently, notwithstanding load variation, for example when the vehicle travels up a hill.
Nevertheless the engine cannot operate at its optimum efficiency under all conditions because the gear box provides for change of gear ratios in discrete steps.
Moreover rapid acceleration within any gear ratio can only be achieved by carburetting a fuel rich mixture which is inefficiently utilised by the engine and is wasteful of fuel. Alternatively the engine may be operated at optimum fuel economy but at the expense of slower acceleration.
Embodiments of the present invention provide means of operating such a motor at a more nearly constant fuel consumption and at close to optimum engine efficiency, while permitting periods of vehicle acceleration at a rate which is independent of engine speed of revolution.
Furthermore embodiments of the invention provide a more or less continuously variable torque conversion in transmission of power from a prime mover to a load and may be used in substitution for a gear box.
In some embodiments it is possible to deliver more torque to the load than could instantaneously be provided by the prime mover.
According to a first aspect the invention consists in apparatus for use in a drive transmission system comprising:
a pump adapted to be driven to perform work on a medium,
and means repetitively and automatically to unload the pump.
According to a second aspect the invention consists in apparatus for use in a driven transmission system comprising:
a flywheel driven by a prime mover
a pump driven by the flywheel to perform work on a medium and means repetitively to unload the pump whereby to permit acceleration of the flywheel.
According to a third aspect the invention consists in drive transmission means for transmitting power from a prime mover to a load comprising:
a flywheel driven by the prime mover,
a pump driven by the flywheel,
a hydraulic motor powered by the pump,
means repetitively to unload the pump thereby permitting the prime mover repetitively to accelerate the flywheel; and
compensation means to power the hydraulic motor while said pump is unloaded.
According to preferred embodiments of the invention the pump is a positive displacement pump, and more preferably a rotary positive displacement pump, provided with relief galleries which eliminate the seal between pumping elements during a part of each stroke or revolution, whereby the pump is repetitively unloaded.